1. Field of the Invention
The present invention relates generally to methods for testing phase noise in long fiber length at high RF frequencies.
2. Description of the Related Art
Fiber optic communication is well known. Fiber optic (FO) links are used in a number of current technologies, including for transmitting remote radio frequency (RF) signals in various systems, such as X-band phased array radars systems.
For accurate phase noise measurements, a reference path is needed in order to subtract the system phase noise thereby increasing the overall measurement dynamic range of the link. The reference path must have a length virtually identical to that of the device under test (DUT) length. For long length FO links (i.e., 1-10 km), this task is almost impossible to achieve. Additionally, if two different long fibers were used, an additional uncertainty is created because the dispersion characteristics of the two fibers may not be the same.
Thus, there is a need for new and improved systems and methods for testing phase noise in long fiber length at high RF frequencies.